Benefiting from the departure of businessman Herman Cain, U.S. Republican presidential contender Newt Gingrich has widened his lead over his primary rivals, according to a new national poll.

Combo photo shows U.S. Republican presidential contenders Newt Gingrich (L) and Mitt Romney. [Xinhua]

Thirty-seven percent of Republicans and Republican-leaning independents support the former House speaker as the party's nominee, with former Massachusetts Governor Mitt Romney at 22 percent, according to the Gallup poll release Tuesday. All other candidates are in the single digits.

When Gallup last measured Republicans' preferences in mid- November, Gingrich was neck-and-neck with Romney, 22 percent to 21 percent.

While Romney's poll numbers were largely unchanged, Gingrich jumped 15 points within just a couple of weeks. His 37 percent support level is the highest of any candidate Gallup has measured all year.

Gingrich's gain was probably due to the departure of embattled Cain, who was at 16 percent in the previous survey. Cain's name was on the list at the beginning of the latest survey, conducted Dec. 1-5, but was removed following his announcement of dropping out on Dec. 3.

"The 2012 GOP nomination contest stands as one of the most topsy-turvy for the Republicans in the primary-nominating era," Gallup said.

This is the latest in a series of front-runner changes. Gallup polls have shown Texas Governor Rick Perry, Cain, Romney, and now Gingrich as the leader or tied for the lead for the Republican nomination.

Gingrich's lead is especially large among conservative Republicans and those who describe themselves as supporters of the Tea Party movement, with more than twice the level of support of any other candidate, according to the survey.

Still, it's far from clear whether Gingrich's momentum is sustainable and could translate into real votes. Despite the strong momentum Gingrich enjoys now, he is likely to find it more difficult to compete with Romney as the races unfold. An important reason is his lack of campaign funds and sophisticated networks across the country that are needed to encourage voters' participation.